Download The Death of Stars

The Death of Stars
Multiple Choice
Identify the letter of the choice that best completes the statement or answers the question.
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1. The lowest-mass stars cannot become giants because
a. they do not contain helium.
b. they rotate too slowly.
c. they cannot heat their centers hot enough.
d. they contain strong magnetic fields.
e. they never use up their hydrogen.
2. A planetary nebula is
a. the expelled outer envelope of a medium mass star.
b. produced by a supernova explosion.
c. produced by a nova explosion.
d. a nebula within which planets are forming.
e. a cloud of hot gas surround a planet
3. The Chandrasekhar limit tells us that
a. accretion disks can grow hot through friction.
b. neutron stars of more than 3 solar masses are not stable.
c. white dwarfs must contain more than 1.4 solar masses.
d. not all stars will end up as white dwarfs.
e. stars with a mass less than 0.5 solar masses will not go through helium flash.
4. In A.D. 1054, Chinese astronomers observed the appearance of a new star, whose location is now occupied by
a. a globular cluster.
b. a planetary nebulae.
c. a white dwarf.
d. a young massive star.
e. a supernova remnant.
5. Massive stars cannot generate energy through iron fusion because
a. iron fusion requires very high density.
b. stars contain very little iron.
c. no star can get hot enough for iron fusion.
d. iron is the most tightly bound of all nuclei.
e. massive stars supernova before they create an iron core.
6. The theory that the collapse of a massive star's iron core produces neutrinos was supported by
a. the size and structure of the Crab nebula.
b. laboratory measurements of the mass of the neutrino.
c. calculation of models of core collapse.
d. underground counts from solar neutrinos.
e. the detection of neutrinos from the supernova of 1987.
7. A Type I supernova is believed to occur when
a. the core of a massive star collapses.
b. carbon detonation occurs.
c. a white dwarf exceeds the Chandrasekhar limit.
d. the cores of massive stars collapse.
e. neutrinos in a massive star become degenerate and form a shock wave that explodes the
star.
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8. Synchrotron radiation is produced by
a. objects with temperatures below 10,000 K.
b. high-velocity electrons moving through a magnetic field.
c. cold hydrogen atoms in space.
d. the collapsing cores of massive stars.
e. helium flash.
9. A nova is almost always associated with
a. a very massive star.
b. a very young star.
c. a star undergoing helium flash.
d. a white dwarf in a close binary system.
e. a solar like star that has exhausted its hydrogen and helium.
10. The Algol paradox is explained by considering
a. the degenerate nature of the hydrogen on the surface of the white dwarf.
b. that iron is the most tightly bound of all atomic nuclei.
c. the rate of expansion of the shock wave inside the supernova.
d. the rotation rate of a neutron star.
e. mass transfer between the two stars in a binary system.
11. Stars with masses between 0.4 M and 4 M
a. undergo thermonuclear fusion of hydrogen and helium, but never get hot enough to ignite
carbon.
b. undergo thermonuclear fusion of hydrogen, but never get hot enough to ignite helium.
c. produce type-I supernovae after they exhaust their nuclear fuels.
d. produce type-II supernovae after they exhaust their nuclear fuels.
e. undergo carbon detonation.
12. A type-II supernova
a. occurs when a white dwarf's mass exceeds the Chandrasekhar limit.
b. is the result of helium flash.
c. is characterized by a spectrum that shows hydrogen lines.
d. occurs when the iron core of a massive star collapses.
e. c and d
13. The Helix and Egg nebulae are
a. supernova remnants.
b. planetary nebulae.
c. the result of carbon detonation.
d. the result of the collapse of the iron core of each star.
e. nebulae associated with Herbig-Haro objects.
14. Synchrotron radiation is produced
a. in planetary nebulae.
b. by red dwarfs.
c. by massive stars as their iron core collapses.
d. in supernova remnants.
e. by neutrinos
15. When material expanding away from a star in a binary system reaches the Roche surface
a. the material will start to fall back toward the star.
b. all of the material will accrete on to the companion.
c. the material is no longer gravitationally bound to the star.
d. the material will increase in temperature and eventually undergo thermonuclear fusion.
e. c and d
____ 16. As material leaves an expanding star and begins to fall into a white dwarf
a. an accretion disk will form around the white dwarf.
b. the material will cool off because it begins to move at high velocities.
c. the material will fall directly onto the surface of the white dwarf.
d. the white dwarf will produce a type-II supernova.
e. the white dwarf's radius will increase.
____ 17. A white dwarf is composed of
a. hydrogen nuclei and degenerate electrons.
b. helium nuclei and normal electrons.
c. carbon and oxygen nuclei and degenerate electrons.
d. degenerate iron nuclei.
e. a helium burning core and a hydrogen burning shell.
____ 18. A planetary nebula
a. produces an absorption spectrum.
b. produces an emission spectrum.
c. is contracting to form planets.
d. is contracting to form the star.
e. is the result of carbon detonation in a 1 M .
____ 19. If the theory that novae occur in close binary systems is correct, then novae should
a. produce synchrotron radiation.
b. occur in regions of star formation.
c. not occur in old star clusters.
d. all be visual binaries.
e. repeat after some interval.
____ 20. A typical planetary nebula will be visible for about
a. 50 years.
b. 500 years.
c. 50,000 years.
d. 5,000,000 years.
e. 5 billion years.
____ 21. We know that the central object in a planetary nebula has a surface temperature of at least _______________
K because the nebula contains large amounts of ionized hydrogen.
a. 5000 K
b. 10,000 K
c. 15,000 K
d. 20,000 K
e. 25,000 K
____ 22. The diagram below shows a light curve from a supernova. How many days after maximum light did it take for
the supernova to decrease in brightness by a factor of 100?
a. 25
b. 50
c. 100
d. 150
e. 250
____ 23. As a white dwarf cools its radius does not change because
a. pressure due to nuclear reactions in a shell just below the surface keeps it from collapsing.
b. pressure does not depend on temperature for a white dwarf because the electrons are
degenerate.
c. pressure does not depend on temperature because the white dwarf is too hot.
d. pressure does not depend on temperature because the star has exhausted all its nuclear
fuels.
e. material accreting onto it from a companion maintains a constant radius.
____ 24. A supernova remnant is expanding in radius at the rate of 0.5 seconds of arc per year. Doppler shifts show
that the velocity of expansion is 5700 km/sec. How far away is the supernova remnant?
a. 1140 pc
b. 11,400 km
c. 5700 pc
d. 24 pc
e. 2400 pc
____ 25. Suppose that a planetary nebula is 0.5 parsecs in diameter and expanding at 20 km/s. How old is it? (Hint: 1
pc = 3.1 1013 km.)
a. 25,000 years
b. 12,000 years
c. 6,000 years
d. 49,000 years
e. 100,000 years
True/False
Indicate whether the sentence or statement is true or false.
____ 26. Planetary nebulae are sites of planet formation.
____ 27. Stars less massive than 0.4 solar mass never become giant stars.
____ 28. Once a star ejects a planetary nebula, it becomes a white dwarf.
____ 29. No known white dwarf has a mass greater than the Chandrasekhar limit.
____ 30. Because massive stars have more gravitational energy than the sun, they can fuse heavier nuclear fuels.
____ 31. The sun will eventually become a supernova.
____ 32. Type II supernovae are believed to occur when the core of a massive star collapses.
____ 33. Synchrotron radiation occurs when high speed electrons move through a magnetic field.
____ 34. A Type II supernova produces a planetary nebula.
____ 35. An accretion disk can grow hot enough to radiate X rays.
____ 36. A nova destroys the star and leaves behind a white dwarf.
Answer Section
MULTIPLE CHOICE
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